The agent/s which make/s free atmospheric nitrogen available to plants is/are:

Select the correct option for the following matches:

$(1)$ For healthy growth of plants	$(a)$ Nitrogen
$(2)$ As a part of vitamins	$(b)$ Manganese
$(3)$ In enzymes associated with fat metabolism	$(c)$ Cobalt
$(4)$ For the activity of phosphatase enzyme	$(d)$ Magnesium

Which of the following organisms does not fix $N_2$?

Select the correct match for $X$ and $Y$.

Column $X$	Column $Y$
$(1)$ Muscle contraction	$(P)$ $Mg^{+2}$
$(2)$ Digestion of food	$(Q)$ $Ca^{+2}$
$(3)$ Energy exchange	$(R)$ $Mo$
$(4)$ Carbohydrate synthesis	$(S)$ $PO_4^{-3}$
$(5)$ Nitrogen fixation	$(T)$ $Cl^{-}$

Nitrogen is required mainly by which of the following parts of the plants?
$I.$ Meristematic tissues
$II.$ Differentiating tissues
$III.$ Apical tissues
$IV.$ Metabolically active cells
Choose the correct option.

Which of the following plants are used as green manure in crop fields and in sandy soils?